Density functional theory study on the mechanism of CO sensing on Cu2O (1 1 1) surface: Influence of the pre-adsorbed oxygen atom

The adsorption of CO molecule on the Cu2O (1 1 1) surface with or without pre-adsorbed oxygen atom (Oad) has been investigated using density functional theory calculation. Calculations show that the adsorption of Oad causes obvious changes in the electronic structure and charge distribution of Cu2O with a charge transfer of 0.48 e from substrate to Oad. On the perfect Cu2O (1 1 1) surface, the one-fold coordinated copper (Cu1c) atom is the most favorable site for the adsorption of CO with a charge transfer of 0.414 e from CO molecule to substrate. Moreover, it is found that the adsorption of CO on the O pre-adsorbed Cu2O (1 1 1) surface is strengthened. The adsorbed CO molecule tends to interact with Oad atom and release the electrons trapped by the oxygen adatom back to the substrate, resulting in a significant charge variation (0.619 e). All these findings indicate that Cu2O would be a good candidate for the detection of CO gas.